JPH0728033B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a semiconductor device in which a SiO ₂ film is formed on a Si substrate.
The present invention relates to a manufacturing method for reducing the Si-SiO ₂ interface state density.

(B) Conventional technology MOS in which the gate electrode is formed on the Si substrate via the SiO ₂ film
In the semiconductor device, the interface state at the Si-SiO ₂ interface causes carrier generation and recombination, causing fluctuations in the channel current. Therefore, the interface state density has a great influence on the characteristics of the semiconductor device. This interface state density depends on the crystal plane orientation of the Si substrate and varies greatly depending on the method of forming the SiO ₂ film and the subsequent heat treatment. This is important when considering the improvement of the refresh time of the memory device of the type.

FIG. 2 is a sectional view showing a part of the CCD solid-state imaging device. On the Si substrate (1) is, Poly-Si electrode having a two-layer structure through the SiO ₂ layer (2) (3) is formed, covered with further SiO ₂ layer (2). Then, contact holes (4) and (5) are provided at predetermined positions of the SiO ₂ layer (2), and the Si substrate (1) and Poly-Si are provided through the contact holes (4) and (5).
Al wirings (6) and (7) are formed on the electrode (3). Such a CCD solid-state image pickup device is used in a gas containing hydrogen, for example, in a mixed gas of H ₂ and N ₂ after forming Al wirings (6) and (7).
By performing heat treatment at about 400 ° C and supplying hydrogen atoms to the Si substrate (1) surface through the SiO ₂ layer (2) and Al wiring (6) as indicated by the broken line in the figure, the interface state density can be reduced. Planned. That is, the interface state density of the Si substrate (1) surface
This is due to the unsaturated bond of Si. By supplementing this unsaturated bond with hydrogen atom, the interface state density can be reduced.

(C) Problems to be Solved by the Invention However, even if the element is heat-treated in a mixed gas of H ₂ and N ₂ , it is still sufficient depending on the thickness of the SiO ₂ layer (2) and the Al wiring (6). Since hydrogen atoms cannot be incorporated into, the interface state density cannot be reduced so much. Furthermore, since heat treatment requires a long time, throughput is reduced,
Not suitable for mass production.

Therefore, an object of the present invention is to provide a manufacturing method capable of effectively supplying hydrogen or a halogen group element which changes to hydrogen to the surface of a silicon substrate.

(D) Means for Solving the Problems The present invention is for solving the above-mentioned problems, and includes a step of forming a gate electrode on a silicon substrate through a silicon oxide layer, and covering the gate electrode with the silicon oxide layer. After that, a step of forming an aluminum wiring connected to the silicon substrate or the gate electrode, a step of forming an insulating film containing hydrogen covering the gate electrode and the aluminum wiring, and a step of forming an aluminum layer on the insulating film And a step of supplying hydrogen to the surface of the silicon substrate by heating in an atmosphere containing hydrogen gas for several hours, and a step of selectively removing the aluminum layer.

(E) Action According to the present invention, hydrogen atoms in the insulating film are supplied to the surface of the silicon substrate by forming an aluminum layer on the insulating film containing hydrogen and then performing heat treatment in an atmosphere containing hydrogen. At the same time, decomposition of hydrogen molecules (H ₂ ) into hydrogen atoms (2H) is promoted on the surface of the aluminum layer, and the hydrogen atoms are supplied to the surface of the silicon substrate through the aluminum layer.

Further, even when a halogen group such as fluorine or chlorine is used instead of hydrogen, the halogen group atoms are supplied to the surface of the silicon substrate by the same operation.

(F) Embodiment An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view in order of the steps, showing the manufacturing process of the present invention, and showing the same portion as FIG.

First, as shown in FIG. 1 (a), SiO _{2 is formed} on the Si substrate (1).
A Poly-Si electrode (3) having a two-layer structure is formed via the layer (2), and Al wirings (6) and (7) are further formed via the SiO ₂ layer (2).

Then, as shown in FIG. 1 (b), Al wiring (6)
A Si ₃ N ₄ layer (10) containing hydrogen atoms (H) is formed on the SiO ₂ layer (2) so as to cover (7). The Si ₃ N ₄ layer (10) is formed to have a layer thickness of about 1 μm by a plasma CVD method, for example.

Then, as shown in FIG. 1 (c), A is deposited on the Si ₃ N ₄ layer (10).
forming a layer (11). Normally, Al wiring (6) (7) connected to the gate electrode (3) and Si substrate (1) is made of Al containing a small amount of Si, but the Al layer (11) formed here.
Is preferably Al containing no impurities such as Si and Cu. That is, Al
If the layer (11) contains impurities such as Si, impurities may precipitate during the heat treatment described later. To prevent this, Al free from impurities is used to form the Al layer (11). To form.

Furthermore, by heating to 400 ° C. in a mixed gas of H ₂ and N ₂ and performing heat treatment for several hours, hydrogen atoms are supplied to the surface of the Si substrate (1) to reduce the interface state density. To do. In this heat treatment, the hydrogen atoms contained in the Si ₃ N ₄ layer (10) are supplied to the surface of the Si substrate (1) through the Al wiring (6) or the SiO ₂ layer (2), and H ₂ is decomposed into hydrogen atoms and supplied to the surface of the Si substrate (1) through the Al layer (11), Si ₃ N ₄ layer (10) and Al wiring (6). On the surface of the Al layer (11), decomposition of H ₂ is promoted, so that hydrogen atoms can be sufficiently incorporated into the Al layer (11).

The Al layer (11) is selectively removed as necessary after the heat treatment. The removal method is preferably wet etching using, for example, phosphoric acid, nitric acid and acetic acid as an etching solution in order to prevent damage due to ion bombardment generated in plasma etching.

According to the above method, by selectively forming the Al layer (11) formed on the Si ₃ N ₄ layer (10), the same Si substrate (1) is formed.
It is also possible to reduce the interface state density only in the specific region above. That is, when the above heat treatment is performed without forming the Al layer (11), the decomposition of H _{2 in} the mixed gas becomes insufficient, the supply of hydrogen atoms from the mixed gas decreases, and the interface state density is reduced. Since it cannot be reduced, the Al layer (11) may be selectively removed in a region inconvenient to reduce the interface state density before the heat treatment.

In addition, in this example, the case where hydrogen is contained in the mixed gas used in the heat treatment and the Si ₃ N ₄ layer (10) is illustrated, but in addition to this, fluorine, chlorine, etc. Even if the halogen group element is used, the interface state density can be similarly reduced. However, since the halogen group element has a larger atomic weight than hydrogen, it is difficult to reach the Si substrate (1) surface,
The effect becomes smaller.

Further, in this embodiment, the Al wiring (6) and the Al layer (11) are made of Si.
_The case of insulation by the ₃ N ₄ layer (10) is shown, but if necessary, a space may be provided in the Si ₃ N ₄ layer (10) to form Al wiring (6) and Al.
It may be connected to the layer (11). In this case, the Si ₃ N ₄ layer (1
Since there is no intervening portion (0), hydrogen atoms that easily pass through the metal easily reach the surface of the Si substrate (1) from the Al layer (11) through the Al wiring (6).

(G) Effect of the Invention According to the present invention, it is possible to efficiently reduce the interface state density of a semiconductor device in which a SiO ₂ layer is formed on a Si substrate. For example, when applied to a CCD solid-state imaging device, dark current If it is applied to a dynamic memory element, the refresh time can be improved.

In addition, the Si ₃ N ₄ layer (10) is used for other insulating layers such as SiO ₂ ,
PSG or the like may be used.

[Brief description of drawings]

FIG. 1 is a sectional view in order of steps showing a method for manufacturing a semiconductor device of the present invention, and FIG. 2 is a sectional view showing an example of a conventional semiconductor device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/339 21/8242 27/108 29/78 7514-4M H01L 29/78 301 Y

Claims (2)

[Claims] 1. A step of forming a gate electrode on a silicon substrate via a silicon oxide layer, a step of covering the gate electrode with a silicon oxide layer, and then forming an aluminum wiring connected to the silicon substrate or the gate electrode, A step of forming an insulating film containing hydrogen over the gate electrode and the aluminum wiring; a step of forming an aluminum layer on the insulating film; heating for several hours in an atmosphere containing hydrogen gas; And a step of selectively removing the aluminum layer, the method of manufacturing a semiconductor element. 2. The method of manufacturing a semiconductor device according to claim 1, wherein fluorine, chlorine or other halogen group is supplied to the surface of the silicon substrate in place of the hydrogen. .